It's just a bit of irony/idiosyncrasy introduced by this particular idiom/symbolism that has developed in the English language.
Standing could mean just sort of just "being passive", it can also mean being willing to fight in what you believe in. And in fighting, unless you truly are as durable as Superman, not moving is generally a bad option. And depending on the types of enemies you face (like most of the ones in both AVWW 1 & 2), effective fighting means moving more often than not.